Systems and methods for detecting turn-to-turn faults in windings

ABSTRACT

Embodiments of the disclosure relate to detecting turn-to-turn faults in one or more windings of various objects. In one implementation, a fault detector uses a differential protection algorithm to detect a turn-to-turn fault in a winding of a three-phase shunt reactor. Various voltage and current measurements carried out upon the three-phase shunt reactor are used to calculate a difference value between a voltage-based parameter and a current-based parameter. The voltage-based parameter is indicative of a normalized negative voltage imbalance and the current-based parameter is indicative of a normalized negative current imbalance. A turn-to-turn winding fault is declared when the difference value is not equal to zero.

FIELD OF THE DISCLOSURE

This disclosure relates to winding fault detectors, and moreparticularly, to turn-to-turn winding fault detector systems andmethods.

BACKGROUND OF THE DISCLOSURE

Winding coils are incorporated into a wide variety of products, forexample, into inductors and transformers. More particularly, inelectrical power transmission systems, various components, for example,a power transformer or a shunt reactor, can include one or more windingcoils. Various types of faults can occur in these windings when in use.Some of these faults, for example, a short circuit between the outputterminals of a power transformer are more readily detectable than otherfaults such as, an internal short circuit between a few turns of aprimary winding or a secondary winding of the power transformer. Theinternal short circuit between the few turns may not necessarily resultin a significant change in the amount of current being delivered by thepower transformer to a power transmission line that is coupled to thepower transformer. However, if timely remedial action is not taken, sucha fault can eventually develop into a major fault that can severelyimpact power transmission through the power transmission line.

Conventional fault detection devices which are typically configured todetect significant current changes in various types of windings may beunable to effectively detect small turn-to-turn faults in such windings.More particularly, conventional fault detection devices may lackadequate sensitivity to detect changes in low amplitude differentialcurrents that are indicative of turn-to-turn faults. Consequently, somesolutions have been proposed that are directed at detecting turn-to-turnfaults using other techniques. For example, one conventional solutiongenerally pertains to fault detection in a power transformer or powerline by using various phase current measurements to identify a source ofnegative sequence differential current, wherein such a source isindicative of a fault. Another conventional example generally pertainsto a negative sequence differential element that is used to detect afault in an electrical power system by computing a differential betweennegative sequence values derived from a first phase-current measurementand a second phase-current measurement.

Conventional solutions using negative sequence differential currents forfault detection can be impacted by various system imbalance conditionsthat can impact the sensitivity and the reliability of the detectionprocess. Further, even when a fault is detected, the precise location ofthe fault in terms of a particular phase in a multi-phase system may notbe identifiable.

BRIEF DESCRIPTION OF THE DISCLOSURE

Embodiments of the disclosure are directed generally to systems andmethods for detecting turn-to-turn faults in winding.

According to one exemplary embodiment of the disclosure, a three-phasepower line system can include a first power line conductor, a secondpower line conductor, a third power line conductor, a three-phase shuntreactor, a first electrical current monitoring element, a secondelectrical current monitoring element, a third electrical currentmonitoring element, a first voltage monitoring element, a second voltagemonitoring element, a third voltage monitoring element, and a faultdetector. The first power line conductor transfers power in a firstphase, the second power line conductor transfers power in a secondphase, and the third power line conductor transfers power in a thirdphase. The three-phase shunt reactor is coupled to the three-phase powerline system. The first electrical current monitoring element isconfigured to provide a first current measurement based on monitoring afirst phase current flowing through a first winding of the three-phaseshunt reactor. The second electrical current monitoring element isconfigured to provide a second current measurement based on monitoring asecond phase current flowing through a second winding of the three-phaseshunt reactor. The third electrical current monitoring element isconfigured to provide a third current measurement based on monitoring athird phase current flowing through a third winding of the three-phaseshunt reactor. The first voltage monitoring element is configured toprovide a first voltage measurement based on monitoring a first phasevoltage present on the first power line conductor. The second voltagemonitoring element is configured to provide a second voltage measurementbased on monitoring a second phase voltage present on the second powerline conductor. The third voltage monitoring element is configured toprovide a third voltage measurement based on monitoring a third phasevoltage present on the third power line conductor. The fault detector isconfigured to receive and to use each of the first phase currentmeasurement, the second phase current measurement, the third phasecurrent measurement, the first phase voltage measurement, the secondphase voltage measurement, and the third phase voltage measurement todetect a turn-to-turn fault in at least one of the first winding, thesecond winding, or the third winding of the three-phase shunt reactor byexecuting a procedure. The procedure includes calculating a differencevalue between a voltage-based parameter and a current-based parameter,wherein the voltage-based parameter is indicative of a normalizednegative voltage imbalance and the current-based parameter is indicativeof a normalized negative current imbalance, and further includesdeclaring an occurrence of the turn-to-turn fault in at least one of thefirst winding, the second winding, or the third winding of thethree-phase shunt reactor when the difference value is not equal tozero.

According to another exemplary embodiment of the disclosure, aturn-to-turn fault detector can include a first input interface, asecond input interface, a third input interface, a fourth inputinterface, a fifth input interface, a sixth input interface, and atleast one processor. The first input interface is configured to receivea first phase current measurement that is based on monitoring a firstphase current flowing through a first winding of a three-phase shuntreactor, wherein the first winding is coupled to a first power lineconductor of a three-phase power line system. The second input interfaceconfigured to receive a second phase current measurement that is basedon monitoring a second phase current flowing through a second winding ofthe three-phase shunt reactor, wherein the second winding is coupled toa second power line conductor of the three-phase power line system. Thethird input interface configured to receive a third phase currentmeasurement that is based on monitoring a third phase current flowingthrough a third winding of the three-phase shunt reactor, wherein thethird winding is coupled to a third power line conductor of thethree-phase power line system. The fourth input interface configured toreceive a first phase voltage measurement that is based on monitoring afirst phase voltage present on the first power line conductor of thethree-phase power line system. The fifth input interface configured toreceive a second phase voltage measurement that is based on monitoring asecond phase voltage present on the second power line conductor of thethree-phase power line system. The sixth input interface configured toreceive a third phase voltage measurement that is based on monitoring athird phase voltage present on the third power line conductor of thethree-phase power line system. The processor is configured to use eachof the first phase current measurement, the second phase currentmeasurement, the third phase current measurement, the first phasevoltage measurement, the second phase voltage measurement, and the thirdphase voltage measurement to detect a turn-to-turn fault in at least oneof the first winding, the second winding, or the third winding of thethree-phase shunt reactor by executing a procedure that includescalculating a difference value between a voltage-based parameter and acurrent-based parameter, wherein the voltage-based parameter isindicative of a normalized negative voltage imbalance and thecurrent-based parameter is indicative of a normalized negative currentimbalance, and further includes declaring a turn-to-turn fault in atleast one of the first winding, the second winding, or the third windingof the three-phase shunt reactor when the difference value is not equalto zero.

According to yet another exemplary embodiment of the disclosure, amethod for detecting a turn-to-turn fault in a three-phase shunt reactorcoupled to a three-phase power line system can include operations suchas receiving a first phase current measurement that is based onmonitoring a first phase current flowing through a first winding of thethree-phase shunt reactor; receiving a second phase current that isbased on monitoring a second phase current flowing through a secondwinding of the three-phase shunt reactor; receiving a third phasecurrent measurement that is based on monitoring a third phase currentflowing through a third winding of the three-phase shunt reactor;receiving a first phase voltage measurement that is based on monitoringa first phase voltage present on a first power line conductor of thethree-phase power line system; receiving a second phase voltagemeasurement that is based on monitoring a second phase voltage presenton a second power line conductor of the three-phase power line system;receiving a third phase voltage measurement that is based on monitoringa third phase voltage present on a third power line conductor of thethree-phase power line system; and using each of the first phase currentmeasurement, the second phase current measurement, the third phasecurrent measurement, the first phase voltage measurement, the secondphase voltage measurement, and the third phase voltage measurement todetect the turn-to-turn fault in at least one of the first winding, thesecond winding, or the third winding of the three-phase shunt reactor bycalculating a difference value between a voltage-based parameter and acurrent-based parameter, wherein the voltage-based parameter isindicative of a normalized negative voltage imbalance and thecurrent-based parameter is indicative of a normalized negative currentimbalance. A turn-to-turn fault in at least one of the first winding,the second winding, or the third winding of the three-phase shuntreactor is declared when the difference value is not equal to zero.

Other embodiments and aspects of the disclosure will become apparentfrom the following description taken in conjunction with the followingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus described the disclosure in general terms, reference willnow be made to the accompanying drawings, which are not necessarilydrawn to scale, and wherein:

FIG. 1 illustrates an example three-phase power line system that caninclude a turn-to-turn fault detector configured to detect one or moreturn-to-turn faults in a three-phase shunt reactor in accordance with anexemplary embodiment of the disclosure.

FIG. 2 illustrates an example phase diagram pertaining to detecting oneor more turn-to-turn faults in the three-phase shunt reactor shown inFIG. 1 on the basis of phase angle information.

FIG. 3 illustrates an example power transmission system that can includea turn-to-turn fault detector system configured to detect a turn-to-turnfault in a single phase transformer in accordance with another exemplaryembodiment of the disclosure.

FIG. 4 illustrates an example power transmission system that can includea turn-to-turn fault detector system configured to detect a turn-to-turnfault in a three-phase transformer in accordance with another exemplaryembodiment of the disclosure.

FIG. 5 illustrates an example equivalent circuit diagram applicable toeach of the single phase transformers shown in FIG. 3 and thethree-phase transformer shown in FIG. 4.

FIG. 6 illustrates an exemplary turn-to-turn fault detector inaccordance with an exemplary embodiment of the disclosure.

FIGS. 7A and 7B illustrate a flowchart of an example method of using aturn-to-turn fault detector to detect a fault in one or more windings ofa three-phase shunt reactor in accordance with an exemplary embodimentof the disclosure.

FIGS. 8A and 8B illustrate a flowchart of an example method of using aturn-to-turn fault detector to detect a turn-to-turn fault in one ormore windings of a transformer in accordance with another exemplaryembodiment of the disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

The disclosure will be described more fully hereinafter with referenceto the accompanying drawings, in which exemplary embodiments of thedisclosure are shown. This disclosure may, however, be embodied in manydifferent forms and should not be construed as limited to the exemplaryembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will satisfy applicable legal requirements. Likenumbers refer to like elements throughout. It should be understood thatcertain words and terms are used herein solely for convenience and suchwords and terms should be interpreted as referring to various objectsand actions that are generally understood in various forms andequivalencies by persons of ordinary skill in the art. For example, itshould be understood that the word “line” as used herein generallyrefers to an electrical conductor, for example, a wire or an electricalpower cable. Furthermore, the word “example” as used herein is intendedto be non-exclusionary and non-limiting in nature. More particularly,the word “exemplary” as used herein indicates one among severalexamples, and it should be understood that no undue emphasis orpreference is being directed to the particular example being described.

In terms of a general overview, certain embodiments of the systems andmethods described herein are directed to a fault detector that can beused to detect one or more turn-to-turn faults in a coil winding. As isknown, coil windings are ubiquitously incorporated into a wide array ofproducts. However, in the interest of brevity, only two products,specifically a three-phase shunt reactor and a power transformer, areused herein to describe various embodiments and aspects in accordancewith the disclosure.

Attention is first drawn to FIG. 1, which illustrates an examplethree-phase power line system 100 that can include a turn-to-turn faultdetector 120 configured to detect one or more turn-to-turn faults in athree-phase shunt reactor 155 in accordance with an exemplary embodimentof the disclosure. Three-phase power line system 100 can be used topropagate electric power over three power lines 101, 102, and 103 in athree-phase configuration as is known in the art. Each of the threepower lines 101, 102, and 103 can be coupled to the three-phase shuntreactor 155 that is deployed in a manner that is known in the art. Thethree-phase shunt reactor 155 can include three windings that arecollectively coupled to ground via a node 118. A first winding 114 ofthe three windings in the three-phase shunt reactor 155 is coupled tothe power line 101 via a first current monitoring element 125 and afirst isolating switch 140. The first isolating switch 140, which is anexemplary protection element, can be controlled by the turn-to-turnfault detector 120 via a control line 113 in order to isolate the firstwinding 114 from the power line 101 when a turn-to-turn fault isdetected in the first winding 114. A second winding 116 of the threewindings in the three-phase shunt reactor 155 is coupled to the powerline 102 via a second current monitoring element 130 and a secondisolating switch 145. The second isolating switch 145 can be controlledby the turn-to-turn fault detector 120 via the control line 113 (or viaa separate control line that is not shown) in order to isolate thesecond winding 116 from the power line 102 when a turn-to-turn fault isdetected in the second winding 116. A third winding 117 of the threewindings in the three-phase shunt reactor 155 is coupled to the powerline 103 via a third current monitoring element 135 and a thirdisolating switch 150. The third isolating switch 150 can be controlledby the turn-to-turn fault detector 120, via the control line 113 (or viaa separate control line that is not shown) in order to isolate the thirdwinding 117 from the power line 103 when a turn-to-turn fault isdetected in the third winding 117. It should be understood that morethan one of the three optional switches 140, 145, and 150 (each of whichcan be implemented in the form of a relay, for example) can be operatedby the turn-to-turn fault detector 120 when one or more turn-to-turnfaults are detected in one or more of the three windings 114, 116, and117. Furthermore, in place of using the three isolating switches, otherprotection elements and configurations can be used to provide remedialaction upon detecting one or more turn-to-turn faults in one or more ofthe three windings 114, 116, and 117.

The first current monitoring element 125 can be used to monitor thepower line 101 and to output a current measurement that is a scaled-downversion of a first phase current that is routed from the power line 101into the first winding 114 of the three-phase shunt reactor 155 whenthree-phase electric power is being transmitted through the three-phasepower line system 100. The current measurement output of the currentmonitoring element 125 is coupled into the turn-to-turn fault detector120 via a line 109. The second current monitoring element 130 can besimilarly used to monitor the power line 102 and to output a currentmeasurement that is a scaled-down version of a second phase current thatis routed from the power line 102 to the second winding 116 of thethree-phase shunt reactor 155 when three-phase electric power is beingtransmitted through the three-phase power line system 100. The currentmeasurement output of the current monitoring element 130 is coupled intothe turn-to-turn fault detector 120 via a line 111. The third currentmonitoring element 135 can also be similarly used to monitor the powerline 103 and to output a current measurement that is a scaled-downversion of a third phase current that is routed from the power line 103to the third winding 117 of the three-phase shunt reactor 155 whenthree-phase electric power is being transmitted through the three-phasepower line system 100. The current measurement output of the currentmonitoring element 135 is coupled into the turn-to-turn fault detector120 via a line 112.

With further reference to the three-phase shunt reactor 155, in anexemplary embodiment in accordance with the disclosure, the threewindings 114, 116, and 117 can be collectively contained within a singleenclosure. Furthermore, the three windings 114, 116, and 117 can beprovided in various configurations such as, for example, a Δconfiguration or a wye configuration. In another exemplary embodiment inaccordance with the disclosure, each of the three windings 114, 116, and117 can be contained in three separate enclosures. In yet anotherexemplary embodiment in accordance with the disclosure, two or more ofthe three windings 114, 116, and 117 can be contained in a secondenclosure that is different than a first enclosure in which theremaining of the three windings 114, 116, and 117 is contained. In yetanother exemplary embodiment in accordance with the disclosure, one ormore additional windings can be provided in addition to the threewindings 114, 116, and 117. For example, a fourth winding can be coupledbetween the node 118 and ground. The turn-to-fault detector 120 can beused to detect one or more turn-to-turn faults in one or more of thesevarious windings in accordance with the disclosure.

Turning now to other monitoring elements in the three-phase power linesystem 100, a first voltage monitoring element 105 can be used tomonitor the power line 101 and to output a voltage measurement that is ascaled-down version of a first phase voltage present on the power line101 when three-phase electric power is transmitted through thethree-phase power line system 100. The voltage measurement output of thevoltage monitoring element 105 is coupled into the turn-to-turn faultdetector 120 via a line 106. A second voltage monitoring element 115 canbe used to monitor the power line 102 and to output a voltagemeasurement that is a scaled-down version of a second phase voltagepresent on the power line 102 when three-phase electric power istransmitted through the three-phase power line system 100. The voltagemeasurement output of the voltage monitoring element 110 is coupled intothe turn-to-turn fault detector 120 via a line 107. A third voltagemonitoring element 115 can be used to monitor the power line 103 and tooutput a voltage measurement that is a scaled-down version of a thirdphase voltage present on the power line 103 when three-phase electricpower is transmitted through the three-phase power line system 100. Thevoltage measurement output of the voltage monitoring element 115 iscoupled into the turn-to-turn fault detector 120 via a line 108.

The turn-to-turn fault detector 120 includes various elements that willbe described below in more detail using another figure. Operatively, theturn-to-turn fault detector 120 is configured to execute a procedurethat uses a differential protection algorithm to detect one or moreturn-to-turn faults in one or more windings of the three-phase shuntreactor 155. In one example implementation, the procedure includes usingthe voltage measurements provided by the voltage monitoring elements105, 110, and 115, and the current measurements provided by the currentmonitoring elements 125, 130, and 135 to calculate a difference valuebetween a voltage-based parameter and a current-based parameter. Thevoltage-based parameter is indicative of a normalized negative voltageimbalance and the current-based parameter is indicative of a normalizednegative current imbalance. The procedure further includes declaring anoccurrence of the turn-to-turn fault in at least one of the firstwinding 114, the second winding 116, or the third winding 117 of thethree-phase shunt reactor 155 when the difference value is not equal tozero. The difference value is approximately zero under steady stateconditions and no turn-to-turn fault is present in the three windings114, 116, and 117. Any small deviation from zero can be attributed tominor system imbalances that may be present under normal operatingconditions of the three-phase power line system 100. In some exemplaryimplementations, the occurrence of the turn-to-turn fault can bedeclared only when the difference value exceeds a threshold value.

Significantly, and in contrast to conventional turn-to-turn faultdetection systems, the turn-to-turn fault detector 120 can be used toidentify a specific faulty phase among the various phases of a targetobject, for example, among the three phases in the three-phase powerline system 100. Also, the turn-to-turn fault detector 120 can be usedto identify turn-to-turn faults in various types of windings withoutrequiring impedance information of the windings (for example, impedanceinformation pertaining to any of the three windings 114, 116, and 117)and without requiring information pertaining to a current flow through aneutral winding (not shown) of the three-phase shunt reactor 155.

Furthermore, the turn-to-turn fault detector 120 can provide asatisfactory level of performance under various operational conditionsof the three-phase power line system 100, for example, under normalsystem unbalances, off-nominal system frequencies, off-nominal systemvoltages, during load switching, in the presence of harmonics, and inthe presence of faults external to the three-phase shunt reactor 155.However, in one example implementation, the turn-to-turn fault detector120 is configured to avoid using the differential protection algorithmwhen one or more of the current monitoring elements 125, 130, and 135undergo one or more of a current saturation condition, a current inrushcondition, or an offline condition.

Details pertaining to the differential protection algorithm used by theturn-to-turn fault detector 120 to detect one or more turn-to-turnfaults in one or more windings of the three-phase shunt reactor 155 canbe further understood in view of the following description based onmathematical equations in accordance with the disclosure.I _(A) =V _(A) /Z _(A) ; I _(B) =V _(B) /Z _(B) ; I _(C) =V _(C) /Z_(C);  Equation (1)V _(Neg) _(_) _(Unbal) _(_) _(Normalized)=(V ₂ /V _(t))×100%  Equation(2)I _(Neg) _(_) _(Unbal) _(_) _(Normalized)=(I ₂ /I ₁)×100%  Equation (3)I _(Neg) _(_) _(Unbal) _(_) _(Normalized)=(I _(A) +a ² I _(B) +aI_(C))/(I _(A) +aI _(B) +a ² I _(C))×100%=[V _(A) /Z _(A) +a ²(V _(B) /Z_(B))+a(V _(C) /Z _(C))]/[V _(A) /Z _(A) +a(V _(B) /Z _(B))+a ²(V _(C)/Z _(C))]×100%   Equation (4)

where V_(A), V_(B), and V_(C) are phase voltage measurements provided tothe turn-to-turn detector 120 by the voltage monitoring elements 105,110, and 115 respectively; I_(A), I_(B), and I_(C) are phase currentmeasurements provided to the turn-to-turn detector 120 by the currentmonitoring elements 125, 130, and 135; Z_(A), Z_(B), and Z_(C) are phaseimpedances of the three windings 114, 116, and 117 of the three-phaseshunt reactor 155; V₂ and V₁ are negative sequence and positive sequencevoltages respectively; and I₂ and I₁ are negative sequence and positivesequence currents respectively. The operator “a” is defined as a unitvector at an angle of 120 degrees, and can be described as “a”=1∠120degrees.

The three windings 114, 116, and 117 of the three-phase shunt reactor155 are typically identical to one another and have a symmetricalarrangement. Consequently, when the three-phase power line system 100 isoperating in a steady state, Z_(A)=Z_(B)=Z_(C)=Z. Thus, from equations(1) through (4), it can be understood that:I _(Neg) _(_) _(Unbal) _(_) _(Normalized) =[V _(A) /Z+a ²(V _(B) /Z)+a(V_(C) /Z)]/[V _(A) /Z+a(V _(B) /Z)+a ²(V _(C) /Z)]×100%=(V _(A) +a ² V_(B) +aV _(C))/(V _(A) +aV _(B) a ² V _(C))×100%=(V ₂ /V ₁)×100%=V_(Neg) _(_) _(Unbal) _(_) _(Normalized)  Equation (5)

where V_(Neg) _(_) _(Unbal) _(_) _(Normalized) and I_(Neg) _(_) _(Unbal)_(_) _(Normalized) are unit-less complex quantities expressed in apercentage form.

A difference value can now be defined in the form of a variable “Diff”as follows:Diff=V _(Neg) _(_) _(Unbal) _(_) _(Normalized) −I _(Neg) _(_) _(Unbal)_(_) _(Normalized)  Equation (6)

Because Z_(A)=Z_(B)=Z_(C)=Z during steady state operation,Diff_(steady)=0 or Diff_(steady)≈0  Equation (7)

When a turn-to-turn faults is present in one of the three windings 114,116, and 117 of the three-phase shunt reactor 155, an impedance of thewinding having the turn-to-turn fault changes, thereby resulting in:V _(Neg) _(_) _(Unbal) _(_) _(Normalized) −I _(Neg) _(_) _(Unbal) _(_)_(Normalized)=Diff  Equation (8)

An absolute value of the difference parameter (Diff) can be used by theturn-to-turn fault detector 120 to declare a fault condition. In oneexample implementation, a fault condition can be declared when theabsolute value of the difference parameter (Diff) exceeds a thresholdpercentage value “c.” The threshold percentage value “c” can be asettable threshold value that can be set by an operator of theturn-to-turn fault detector 120.Fault condition=abs(Diff−Diff_(steady))>c  Equation (9)

A fault condition can also be declared by examining vectorrepresentations of phases associated with each of the voltages V_(A),V_(B), and V_(C). In one exemplary embodiment, this can be carried outby using the expression ∠(Diff−Diff_(steady)). A faulty “phase A” may bedeclared when ∠(Diff−Diff_(steady)) is in a range of 180°±D, a faulty“phase B” may be declared when ∠(Diff−Diff_(steady)) is in a range of−60°±D, and a faulty “phase C” may be declared when∠(Diff−Diff_(steady)) is in a range of +60 degrees±D, where “D” is alimit angle that can be set in a range of 20° to 60°.

FIG. 2 illustrates an example phase diagram 200 pertaining to detectingone or more turn-to-turn faults in the three-phase shunt reactor 155 onthe basis of phase angle information. The range of 180 degrees±Dcorresponding to “phase A” is indicated by an arrow 205, the range of−60 degrees±D corresponding to “phase B” is indicated by an arrow 210,and the range of +60 degrees±D corresponding to “phase C” is indicatedby an arrow 215. The turn-to-turn fault detector 120 can be configuredto declare a fault in a particular phase among the three phases A, B,and C by employing the three ranges shown in the example phase diagram200.

FIG. 3 illustrates an example power transmission system 300 that caninclude a turn-to-turn fault detector system 120 configured to detect aturn-to-turn fault in the primary and secondary windings of a singlephase transformer 310 in accordance with another exemplary embodiment ofthe disclosure. A first current monitoring element 305 can be used tomonitor a primary current “I_(P)” that flows via line 306 and into aprimary winding of the single phase transformer 310. The first currentmonitoring element 305 provides a scaled-down version of the primarycurrent to the turn-to-turn fault detector 120 via a line 301. A secondcurrent monitoring element 315 can be used to monitor a secondarycurrent “I_(S)” that flows out to a line 307 from a secondary winding ofthe single phase transformer 310. The second current monitoring element315 provides a scaled-down version of the secondary current to theturn-to-turn fault detector 120 via a line 302. Additional monitoringelements (not shown) can be used for monitoring voltages at variousnodes of the power transmission system 300, such as, for example, toprovide the turn-to-turn fault detector 120 with one or moresteady-state voltage values or differential voltage values associatedwith the primary winding and the secondary winding of the single phasetransformer 310.

In this exemplary embodiment, the turn-to-turn fault detector 120 isconfigured to execute a procedure that includes using the current valuesand the voltage values obtained via the various monitoring elements todetermine various steady-state differential currents and varioussteady-state voltage values. Each of the steady-state differentialcurrents typically includes a steady-state magnetizing current componentthat is dependent upon at least one steady-state voltage that is presentat a terminal of the single phase transformer 310.

In accordance with this disclosure, and in contrast to conventionalimplementations, one or more compensating factors (in the form of one ormore modifier values) are combined with the various steady-statedifferential current values to compensate for the steady-statemagnetizing current component and also to compensate for any measurementerrors in the steady-state differential current values. In one exampleimplementation, a modifier value that is equal to a magnetizing currentcomponent value can be used. The modifier value may be subtracted from asteady-state differential current value to provide the compensation.

The compensated steady-state differential current value can then be usedto detect a turn-to-turn fault, such as, for example, by comparing acompensated steady-state differential current value against a referencethreshold value. The comparing may be carried out over a pre-settableperiod of time that can be pre-set by an operator, for example.

Upon detection of a turn-to-turn fault, the turn-to-turn fault detector120 can carry out a remedial action. For example, the turn-to-turn faultdetector 120 can provide a first control signal (via a line 303) to afirst protection element 320 (a relay, for example) in order to isolatethe primary winding of the single phase transformer 310 from the powerline conductor 306. As another example, the turn-to-turn fault detector120 can provide a second control signal (via a line 304) to a secondprotection element 325 (another relay, for example) in order to isolatethe secondary winding of the single phase transformer 310 from the powerline conductor 307. The turn-to-turn fault detector 120 can also providea fault indicator signal via a line 308, to a fault monitoring unit (notshown) such as, for example, a computer that is located at a monitoringstation, a display device located at the monitoring station, or an alarm(light, buzzer, siren etc.) located on or near the turn-to-turn faultdetector 120.

FIG. 4 illustrates a power transmission system 400 that can include aturn-to-turn fault detector system 120 configured to detect aturn-to-turn fault in a three-phase transformer 410 in accordance withanother exemplary embodiment of the disclosure. In this other exemplaryembodiment, the three-phase transformer 410 is shown with three primarywindings interconnected in a “Δ” arrangement and three secondarywindings interconnected in a “Y” arrangement, solely as a matter ofconvenience for purposes of description. However, it should beunderstood that the description provided below in accordance with thedisclosure, is equally applicable to various other configurations andinterconnections associated with the three three-phase transformer 410.

A first current monitoring element 405 can be used to monitor a phase“A” primary current “I_(AP)” that flows via line 401 into a firstprimary winding of the three-phase transformer 410. The first currentmonitoring element 405 provides to the turn-to-turn fault detector 120,via a line 404, a scaled-down version “I_(ap)” of the primary current“I_(AP).” A second current monitoring element 420 can be used to monitora phase “B” primary current “I_(BP)” that flows via line 402 into asecond primary winding of the three-phase transformer 410. The secondcurrent monitoring element 420 provides to the turn-to-turn faultdetector 120, via a line 406, a scaled-down version “I_(bp)” of theprimary current “I_(BP).” A third current monitoring element 435 can beused to monitor a phase “C” primary current “I_(CP)” that flows via line403 into a third primary winding of the three-phase transformer 410. Thethird current monitoring element 435 provides to the turn-to-turn faultdetector 120, via a line 407, a scaled-down version “I_(cp)” of theprimary current “I_(CP).”

A fourth current monitoring element 415 can be used to monitor a phase“A” secondary current “I_(AS)” that is provided by a first secondarywinding of the three-phase transformer 410 to a line 413. The fourthcurrent monitoring element 415 provides to the turn-to-turn faultdetector 120, a first secondary current measurement “I_(as)” that is ascaled-down version of “I_(AS).” A fifth current monitoring element 430can be used to monitor a phase “B” secondary current “I_(BS)” that isprovided by a second secondary winding of the three-phase transformer410 to a line 414. The fifth current monitoring element 430 provides tothe turn-to-turn fault detector 120, a second secondary currentmeasurement “I_(bs)” that is a scaled-down version of “I_(BS).” A sixthcurrent monitoring element 445 can be used to monitor a phase “C”secondary current “I_(CS)” that is provided by a third secondary windingof the three-phase transformer 410 to a line 416. The sixth currentmonitoring element 445 provides to the turn-to-turn fault detector 120,a third secondary current measurement “I_(cs)” that is a scaled-downversion of “I_(CS).” In this exemplary embodiment, the three secondarycurrent measurements (“I_(as),” “I_(bs),” and “I_(cs)”) are coupled intothe turn-to-turn fault detector 120 via a line arrangement that includesline 408, line 409, and line 411.

Additional monitoring elements (not shown) can be used for monitoringvoltages at various nodes of the power transmission system 400, forexample, to provide the turn-to-turn fault detector 120 with one or moresteady-state voltage values or differential voltage values associatedwith one or more of the three primary windings and the three secondarywindings of the three-phase transformer 410.

The turn-to-turn fault detector 120 is configured to execute a procedurethat includes using the current values and the voltage values obtainedvia the various monitoring elements described above to determine varioussteady-state differential currents and various steady-state voltagevalues. This procedure can be understood in view of the proceduredescribed above with reference to FIG. 3 and further in view of thefollowing description based on mathematical equations in accordance withthe disclosure.Idiff_A_compensated=Idiff_A−KA*V _(RA)  Equation (10)Idiff_B_compensated=Idiff_B−KA*V _(RB)  Equation (11)Idiff_C_compensated=Idiff_C−KA*V _(RC)  Equation (12)

where V_(RA), V_(RB), and V_(RC) are the phase A, phase B, and phase Cvoltages on the output side of the three-phase transformer 410. However,in alternative implementations, the phase A, phase B, and phase Cvoltages on the input side of the three-phase transformer 410 can beused instead. KA, KB, and KC are coefficients that are used during asteady state operation of the three-phase transformer 410 in order tomake each of Idiff_A_compensated, Idiff_B_compensated, andIdiff_C_compensated equal to zero. One or more of each ofIdiff_A_compensated, Idiff_B_compensated, and Idiff_C_compensated willincrease to a value greater than zero when a turn-to-fault exists in oneor more of the respective windings. The coefficients KA, KB, and KC canbe defined as follows:KA=Idiff_A_steady/V _(RA) steady  Equation (13)KB=Idiff_A_steady/V _(RB) steady  Equation (14)KC=Idiff_A_steady/V _(RC) steady  Equation (15)

An absolute value of each of Idiff_A_compensated, Idiff_B_compensated,and Idiff_C_compensated can be used by the turn-to-turn fault detector120 to declare a fault condition in a respective phase of thethree-phase transformer 410. In one example implementation, a faultcondition can be declared in phase A when the absolute value ofIdiff_A_compensated exceeds (or equals) a threshold percentage value“a,” a fault condition can be declared in phase B when the absolutevalue of Idiff_B_compensated exceeds (or equals) a threshold percentagevalue “b,” and a fault condition can be declared in phase C when theabsolute value of Idiff_C_compensated exceeds (or equals) a thresholdpercentage value “c.” In other words, a turn-to-turn fault condition inphase A is declared when abs(Idiff_A_compensated)≥“a,” a turn-to-turnfault condition in phase B is declared whenabs(Idiff_B_compensated)≥“b,” and a turn-to-turn fault condition inphase C is declared when abs(Idiff_C_compensated)≥“c.” The thresholdpercentage values “a,” “b,” and “c” can be settable threshold valuesthat can be set, for example, by an operator of the turn-to-turn faultdetector 120.

Upon detection of a turn-to-turn fault in the three-phase transformer410, the turn-to-turn fault detector 120 can carry out a remedialaction. For example, the turn-to-turn fault detector 120 can provide acontrol signal (via a line 412) to one or more protection elements (notshown) in order to isolate one or more of the primary windings from arespective one or more input lines, and/or to isolate one or more of thesecondary windings from a respective one or more output lines. In someexample implementations, the turn-to-turn fault detector 120 can providea fault indicator signal via the line 412 to a fault monitoring unit(not shown) such as, for example, a computer that is located at amonitoring station, a display device located at the monitoring station,or an alarm (light, buzzer, siren etc.) located on or near theturn-to-turn fault detector 120.

FIG. 5 illustrates an example equivalent circuit diagram of the singlephase transformer 310 shown in FIG. 3. The input current I₁ is equal tothe output current I₂ (typically with a phase difference of 180°) if noloss were to be incurred in the single phase transformer 310. However,in practicality, a current loss does occur in the single phasetransformer 310. This current loss can be attributed to a magnetizingcurrent I₀ that is shown in the equivalent circuit diagram. Theturn-to-turn fault detector 120 carries out a fault-to-fault detectionby taking this magnetizing current I₀ into consideration in accordancewith the disclosure.

FIG. 6 illustrates some exemplary elements that can be contained in theturn-to-turn fault detector 120 in accordance with the disclosure. Forpurposes of description, the turn-to-turn fault detector 120 shown inFIG. 6 contains various elements that can be used for implementing theexemplary embodiment shown in FIG. 4 and described above with respect tothe three-phase transformer 410. Accordingly, the input lines and outputlines are designated by the same reference numerals that are shown inFIG. 4. However, in other implementations, such as, for example, whenimplementing the single phase transformer 310 embodiment shown in FIG.3, the number of various elements (such as, for example, the number ofinput interfaces) contained in the turn-to-turn fault detector 120 canbe different.

In this exemplary implementation, the turn-to-turn fault detector 120can include six input current interfaces 605, 625, 645, 620, 640 and 660that are coupled to lines 404, 406, 407, 408, 409 and 411 respectively.Other input interfaces, such as for example voltage input interfaces(not shown) can be used for providing the turn-to-turn fault detector120 with various kinds of voltage measurement inputs. The turn-to-turnfault detector 120 can also include one or more output interfaces (suchas an output interface 665 that is shown coupled to the line 412), forpurposes of transmitting output signals such as a control signal, afault indication signal, or an alarm signal.

The turn-to-turn fault detector 120 can further include one or moreanalog-to-digital converters and digital-to-analog converters. Forexample, the analog-to-digital converter 615 can be used to convert acurrent measurement provided by one of the input interfaces in an analogform into a digital current measurement value that can be processed bythe processor 650. Conversely, the digital-to-analog converter 635 canbe used to convert various types of digital information that can beprovided by the processor 650 to the digital-to-analog converter 635,into an analog output signal that is transmitted out of the turn-to-turnfault detector 120 via the output interface 665. One or more relays,such as a relay 655, can be used for switching various types of signals(such as, for example, certain current signals associated with the powertransmission system 400) when a turn-to-turn fault is detected in thethree-phase transformer 410.

One or more processors, such as the processor 650, can be configured tointeract with a memory 630. The processor 650 can be implemented andoperated using appropriate hardware, software, firmware, or combinationsthereof. Software or firmware implementations can includecomputer-executable or machine-executable instructions written in anysuitable programming language to perform the various functionsdescribed. In one embodiment, instructions associated with a functionblock language can be stored in the memory 630 and executed by theprocessor 650.

The memory 630 can be used to store program instructions that areloadable and executable by the processor 650, as well as to store datagenerated during the execution of these programs. Depending on theconfiguration and type of the turn-to-turn fault detector 120, thememory 630 can be volatile (such as random access memory (RAM)) and/ornon-volatile (such as read-only memory (ROM), flash memory, etc.). Insome embodiments, the memory devices can also include additionalremovable storage (not shown) and/or non-removable storage (not shown)including, but not limited to, magnetic storage, optical disks, and/ortape storage. The disk drives and their associated computer-readablemedia can provide non-volatile storage of computer-readableinstructions, data structures, program modules, and other data. In someimplementations, the memory 630 can include multiple different types ofmemory, such as static random access memory (SRAM), dynamic randomaccess memory (DRAM), or ROM.

The memory 630, the removable storage, and the non-removable storage areall examples of non-transient computer-readable storage media. Suchnon-transient computer-readable storage media can be implemented in anymethod or technology for storage of information such ascomputer-readable instructions, data structures, program modules orother data. Additional types of non-transient computer storage mediathat can be present include, but are not limited to, programmable randomaccess memory (PRAM), SRAM, DRAM, ROM, electrically erasableprogrammable read-only memory (EEPROM), compact disc read-only memory(CD-ROM), digital versatile discs (DVD) or other optical storage,magnetic cassettes, magnetic tapes, magnetic disk storage or othermagnetic storage devices, or any other medium which can be used to storethe desired information and which can be accessed by the processor 650.Combinations of any of the above should also be included within thescope of non-transient computer-readable media.

Turning to the contents of the memory 630, the memory 630 can include,but is not limited to, an operating system (OS) and one or moreapplication programs or services for implementing the features andaspects disclosed herein. Such applications or services can include aturn-to-turn fault detection module (not shown). In one embodiment, theturn-to-turn fault detection module can be implemented by software thatis provided in configurable control block language and is stored innon-volatile memory. When executed by the processor 650, the performanceturn-to-turn fault detection module implements the variousfunctionalities and features described in this disclosure.

FIGS. 7A and 7B illustrate an example flowchart of a method of using aturn-to-turn fault detection to detect a fault in one or more windingsof a three-phase shunt reactor in accordance with an exemplaryembodiment of the disclosure. The three-phase power line system 100shown in FIG. 1 will be used here solely as a matter of convenience todescribe the various operations shown in this example flowchart.

In block 705, a first phase current measurement that is based onmonitoring a first phase current flowing through a first winding of thethree-phase shunt reactor is received. This operation can correspond tothe turn-to-turn fault detector 120 receiving the first phase currentmeasurement via line 109 from the first current monitoring element 125.

In block 710, a second phase current measurement that is based onmonitoring a second phase current flowing through a second winding ofthe three-phase shunt reactor is received. This operation can correspondto the turn-to-turn fault detector 120 receiving the second phasecurrent measurement via line 111 from the second current monitoringelement 130.

In block 715, a third phase current measurement that is based onmonitoring a third phase current flowing through a third winding of thethree-phase shunt reactor is received. This operation can correspond tothe turn-to-turn fault detector 120 receiving the third phase currentmeasurement via line 112 from the third current monitoring element 135.

In block 720, a first phase voltage measurement that is based onmonitoring a first phase voltage present on a first power line conductorof a three-phase power line system is received. This operation cancorrespond to the turn-to-turn fault detector 120 receiving the firstphase voltage measurement via line 106 from the first voltage monitoringelement 105.

In block 725, a second phase voltage measurement that is based onmonitoring a second phase voltage present on a second power lineconductor of a three-phase power line system is received. This operationcan correspond to the turn-to-turn fault detector 120 receiving thesecond phase voltage measurement via line 107 from the second voltagemonitoring element 110.

In block 730, a third phase voltage measurement that is based onmonitoring a third phase voltage present on a third power line conductorof a three-phase power line system is received. This operation cancorrespond to the turn-to-turn fault detector 120 receiving the thirdphase voltage measurement via line 108 from the third voltage monitoringelement 115.

In block 735, the turn-to-turn fault detector uses each of the firstphase current measurement, the second phase current measurement, thethird phase current measurement, the first phase voltage measurement,the second phase voltage measurement, and the third phase voltagemeasurement to detect the turn-to-turn fault in at least one of thefirst winding, the second winding, or the third winding of thethree-phase shunt reactor. The detection is carried out by calculating adifference value between a voltage-based parameter and a current-basedparameter, wherein the voltage-based parameter is indicative of anormalized negative voltage imbalance and the current-based parameter isindicative of a normalized negative current imbalance.

In block 740, the turn-to-turn fault detector declares the turn-to-turnfault in at least one of the first winding, the second winding, or thethird winding of the three-phase shunt reactor when the difference valueis not equal to zero.

FIGS. 8A and 8B illustrate an example flowchart of a method of using aturn-to-turn fault detection to detect a turn-to-turn fault in one ormore windings of a transformer in accordance with an exemplaryembodiment of the disclosure. The power transmission system 300 shown inFIG. 3 will be used solely as a matter of convenience to describe thevarious operations shown in this example flowchart. It should be howeverunderstood that the method can be suitably applied to detect aturn-to-turn fault in one or more windings of a multi-phase transformersuch as the three-phase transformer 410 shown in FIG. 4.

In block 805, a first current measurement that is based on monitoring aprimary winding of a transformer is received. This operation cancorrespond to the turn-to-turn fault detector 120 receiving the firstcurrent measurement via line 301 from the first current monitoringelement 305.

In block 810, a second current measurement that is based on monitoring asecondary winding of a transformer is received. This operation cancorrespond to the turn-to-turn fault detector 120 receiving the secondcurrent measurement via line 302 from the second current monitoringelement 315. In block 815, each of the first current measurement and thesecond current measurement is used to determine a steady-statedifferential current value and a steady-state voltage value. In block820, one or more compensating factors are determined by dividing thesteady-state differential current value by the steady-state voltagevalue. In block 825, a magnetizing current amplitude indicator isdetermined by multiplying the steady-state voltage value with thecompensating factor. In block 830, a compensated differential currentvalue is determined by combining the steady-state differential currentvalue with a modifier value, the modifier value incorporating themagnetizing current amplitude indicator. In block 835, the compensateddifferential current value is compared against a threshold value. Inblock 840, an occurrence of a turn-to-turn fault in the transformer isdeclared when the compensated differential current value exceeds thethreshold value. In block 845, a remedial operation comprising at leastone of transmitting an alarm or operating a protection relay isexecuted. For example, the turn-to-turn fault detector 120 can activatethe first protection element 320 and/or the second protection element325.

In summary, the systems and methods disclosed herein for detectingturn-to-turn faults are not limited exclusively to a three-phase shuntreactor as embodied in the accompanying claims, but are equallyapplicable to various other objects that incorporate one or morewindings. A few example systems and methods that can be associated witha transformer for example, are provided below.

A first exemplary system in accordance with an embodiment of thedisclosure can include a transformer, a first current monitoringelement, a second current monitoring element and a fault detector. Thefirst current monitoring element can be configured to provide a firstcurrent measurement based on monitoring a primary winding current of thetransformer. The second current monitoring element can configured toprovide a second current measurement based on monitoring a secondarywinding current of the transformer. The fault detector can be configuredto receive each of the first current measurement and the second currentmeasurement and to detect using the first current measurement and thesecond current measurement, a turn-to-turn fault in the transformer byexecuting a procedure that can include determining a steady-statedifferential current value, determining a steady-state voltage value,determining one or more compensating factors by dividing thesteady-state differential current value by the steady-state voltagevalue, determining a magnetizing current amplitude indicator bymultiplying the steady-state voltage value by the one or morecompensating factors, determining a compensated differential currentvalue by combining the steady-state differential current value with amodifier value, the modifier value incorporating the magnetizing currentamplitude indicator, comparing the compensated differential currentvalue against a threshold value, declaring an occurrence of theturn-to-turn fault in the transformer when the compensated differentialcurrent value exceeds the threshold value, and executing a remedialoperation comprising at least one of transmitting an alarm or operatinga protection relay.

The modifier value can be equal to the magnetizing current amplitudeindicator. Combining the steady-state differential current value withthe modifier value can include subtracting the modifier value from thesteady-state differential current value. The amplitude of themagnetizing current amplitude indicator can be directly proportional toan amplitude of an operating voltage of the transformer. The occurrenceof the turn-to-turn fault in the transformer can be declared when thecompensated differential current value exceeds the threshold value for apredetermined period of time and the exemplary system can include a userinterface configured to accept a user input indicative of thepredetermined period of time. The transformer can be a multi-phasetransformer and each of the primary winding current and the secondarywinding current can correspond to a first pair of windings among aplurality of windings of the multi-phase transformer and the faultdetector can be configured to detect the turn-to-turn fault when presentin any one of the plurality of windings of the multi-phase transformer.The transformer can be a three-phase transformer having at least twosets of windings and the fault detector can be configured to execute theprocedure for each phase of the three-phase transformer.

A second exemplary system in accordance with an embodiment of thedisclosure can include a multi-phase transformer, an electrical currentmonitoring system, and a fault detector. The electrical currentmonitoring system can be configured to provide a set of primaryelectrical current measurements based on monitoring each of a pluralityof primary winding currents of the multi-phase transformer and a set ofsecondary electrical current measurements based on monitoring each of aplurality of secondary winding currents of the multi-phase transformer.The fault detector can be configured to receive the set of primaryelectrical current measurements and the set of secondary electricalcurrent measurements and to detect using the set of primary electricalcurrent measurements and the set of secondary electrical currentmeasurements, a turn-to-turn fault in the multi-phase transformer byexecuting a procedure that can include determining a steady-statedifferential current value for each phase of the multi-phasetransformer, determining a steady-state differential voltage value foreach phase of the multi-phase transformer, determining one or morecompensating factors by dividing the steady-state differential currentvalue by the steady-state voltage value for each phase of themulti-phase transformer, determining a magnetizing current amplitudeindicator for each phase of the multi-phase transformer by multiplying arespective steady-state voltage value by one or more compensatingfactors, determining a compensated differential current value for eachphase of the multi-phase transformer by combining a respectivesteady-state differential current value with a respective modifiervalue, each respective modifier value incorporating a respectivemagnetizing current amplitude indicator, comparing the compensateddifferential current value for each phase of the multi-phase transformeragainst a threshold value for each phase of the multi-phase transformer,declaring an occurrence of the turn-to-turn fault in the transformerwhen at least one of the compensated differential current values exceedsthe threshold value, and executing a remedial operation comprising atleast one of transmitting an alarm or operating a protection relay.

The respective modifier value can be equal to the respectivemagnetization current amplitude indicator. Combining the respectivesteady-state differential current value with the respective modifiervalue can include subtracting the respective modifier value from therespective steady-state differential current value. The amplitude of therespective magnetizing current amplitude indicator can be directlyproportional to an amplitude of a respective phase operating voltage ofthe transformer. The occurrence of the turn-to-turn fault in thetransformer can be declared when the at least one of the compensateddifferential current values exceeds the threshold value for apredetermined period of time and the exemplary system can include a userinterface configured to accept a user input indicative of thepredetermined period of time. The transformer can be a three-phasetransformer and the fault detector can be configured to detect theturn-to-turn fault when present in any one of the plurality of windingsof the three-phase transformer.

An exemplary method in accordance with an embodiment of the disclosurecan include receiving in a fault detector, a first current measurementbased on monitoring a primary winding current of a transformer,receiving in the fault detector, a second current measurement based onmonitoring a secondary winding current of a transformer, using the firstcurrent measurement and the second current measurement to determine asteady-state differential current value and a steady-state voltagevalue, determining one or more compensating factors by dividing thesteady-state differential current value by the steady-state voltagevalue, determining a magnetizing current amplitude indicator bymultiplying the steady-state voltage value by the one or morecompensating factors, determining a compensated differential currentvalue by combining the steady-state differential current value with amodifier value, the modifier value incorporating the magnetizing currentamplitude indicator, comparing the compensated differential currentvalue against a threshold value, declaring an occurrence of theturn-to-turn fault in the transformer when the compensated differentialcurrent value exceeds the threshold value, and executing a remedialoperation comprising at least one of transmitting an alarm or operatinga protection relay. The modifier value can be equal to the magnetizingcurrent amplitude indicator. Combining the steady-state differentialcurrent value with the modifier value can include subtracting themodifier value from the steady-state differential current value.

Many modifications and other embodiments of the example descriptions setforth herein to which these descriptions pertain will come to mindhaving the benefit of the teachings presented in the foregoingdescriptions and the associated drawings. Thus, it will be appreciatedthe disclosure may be embodied in many forms and should not be limitedto the exemplary embodiments described above. Therefore, it is to beunderstood that the disclosure is not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

That which is claimed is:
 1. A three-phase power line system comprising:a first power line conductor that transfers power in a first phase, asecond power line conductor that transfers power in a second phase, anda third power line conductor that transfers power in a third phase; athree-phase shunt reactor coupled to the three-phase power line system;a first electrical current monitoring element configured to provide afirst current measurement based on monitoring a first phase currentflowing through a first winding of the three-phase shunt reactor; asecond electrical current monitoring element configured to provide asecond current measurement based on monitoring a second phase currentflowing through a second winding of the three-phase shunt reactor; athird electrical current monitoring element configured to provide athird current measurement based on monitoring a third phase currentflowing through a third winding of the three-phase shunt reactor; afirst voltage monitoring element configured to provide a first voltagemeasurement based on monitoring a first phase voltage present on thefirst power line conductor; a second voltage monitoring elementconfigured to provide a second voltage measurement based on monitoring asecond phase voltage present on the second power line conductor; a thirdvoltage monitoring element configured to provide a third voltagemeasurement based on monitoring a third phase voltage present on thethird power line conductor; and a fault detector configured to receiveand to use each of the first phase current measurement, the second phasecurrent measurement, the third phase current measurement, the firstphase voltage measurement, the second phase voltage measurement, and thethird phase voltage measurement to detect a turn-to-turn fault in atleast one of the first winding, the second winding, or the third windingof the three-phase shunt reactor by executing a procedure comprising:calculating a difference value between a voltage-based parameter and acurrent-based parameter, wherein the voltage-based parameter isindicative of a normalized negative voltage imbalance and thecurrent-based parameter is indicative of a normalized negative currentimbalance; and declaring an occurrence of the turn-to-turn fault in atleast one of the first winding, the second winding, or the third windingof the three-phase shunt reactor when the difference value is not equalto zero.
 2. The system of claim 1, wherein the voltage-based parameteris a first normalized value derived at least in part by comparing anegative sequence voltage value to a positive sequence voltage value,and the current-based parameter is a second normalized value derived atleast in part by comparing a negative sequence current value to apositive sequence current value.
 3. The system of claim 2, wherein eachof the negative sequence voltage value and the positive sequence voltagevalue is represented in a vector representation of phase voltagespresent in the three-phase power line system.
 4. The system of claim 2,wherein the first normalized value is indicated as a first percentageand the second normalized value is indicated as a second percentage. 5.The system of claim 2, wherein the first normalized value is equal tothe second normalized value when the turn-to-turn fault is not presentin the three-phase shunt reactor.
 6. The system of claim 2, wherein thefault detector is further configured to execute a remedial operationupon the occurrence of the turn-to-turn fault, the remedial actioncomprising operating a protection relay.
 7. The system of claim 6,wherein the remedial action is executed based on the difference valueexceeding a settable threshold value.
 8. The system of claim 7, whereinthe difference value is defined as at least one of an absolute numericalvalue or an angular value, and the settable threshold value iscorrespondingly based on the at least one of an absolute numerical valueor an angular value.
 9. The system of claim 2, wherein the differencevalue is defined as an angular value, and an identification of theturn-to-turn fault in a particular one of the first winding, the secondwinding, or the third winding of the three-phase shunt reactor isdetermined based on the angular value.
 10. The system of claim 9,wherein the first winding is identified when the angular value issubstantially equal to about (180 degrees±a tolerance value), the secondwinding is identified when the angular value is substantially equal toabout (−60 degrees±the tolerance value), and the third winding isidentified when the angular value is substantially equal to about (+60degrees±the tolerance value).
 11. A turn-to-turn fault detectorcomprising: a first input interface configured to receive a first phasecurrent measurement that is based on monitoring a first phase currentflowing through a first winding of a three-phase shunt reactor, whereinthe first winding is coupled to a first power line conductor of athree-phase power line system; a second input interface configured toreceive a second phase current measurement that is based on monitoring asecond phase current flowing through a second winding of the three-phaseshunt reactor, wherein the second winding is coupled to a second powerline conductor of the three-phase power line system; a third inputinterface configured to receive a third phase current measurement thatis based on monitoring a third phase current flowing through a thirdwinding of the three-phase shunt reactor, wherein the third winding iscoupled to a third power line conductor of the three-phase power linesystem; a fourth input interface configured to receive a first phasevoltage measurement that is based on monitoring a first phase voltagepresent on the first power line conductor of the three-phase power linesystem; a fifth input interface configured to receive a second phasevoltage measurement that is based on monitoring a second phase voltagepresent on the second power line conductor of the three-phase power linesystem; a sixth input interface configured to receive a third phasevoltage measurement that is based on monitoring a third phase voltagepresent on the third power line conductor of the three-phase power linesystem; and at least one processor configured to use each of the firstphase current measurement, the second phase current measurement, thethird phase current measurement, the first phase voltage measurement,the second phase voltage measurement, and the third phase voltagemeasurement to detect a turn-to-turn fault in at least one of the firstwinding, the second winding, or the third winding of the three-phaseshunt reactor by executing a procedure comprising: calculating adifference value between a voltage-based parameter and a current-basedparameter, wherein the voltage-based parameter is indicative of anormalized negative voltage imbalance and the current-based parameter isindicative of a normalized negative current imbalance; and declaring aturn-to-turn fault in at least one of the first winding, the secondwinding, or the third winding of the three-phase shunt reactor when thedifference value is not equal to zero.
 12. The detector of claim 11,wherein the voltage-based parameter is a first normalized value derivedat least in part by comparing a negative sequence voltage value to apositive sequence voltage value, and the current-based parameter is asecond normalized value derived at least in part by comparing a negativesequence current value to a positive sequence current value.
 13. Thedetector of claim 12, wherein each of the negative sequence voltagevalue and the positive sequence voltage value is represented in a vectorrepresentation of phase voltages present in the three-phase power linesystem, the first normalized value is indicated as a first percentageand the second normalized value is indicated as a second percentage. 14.The detector of claim 12, wherein the first normalized value is equal tothe second normalized value when the turn-to-turn fault is not presentin the three-phase shunt reactor.
 15. The detector of claim 12, whereinthe difference value is defined as at least one of an absolute numericalvalue or an angular value, and an identification of the turn-to-turnfault in a particular one of the first winding, the second winding, orthe third winding of the three-phase shunt reactor is determined basedon the at least one of the absolute numerical value or the angularvalue.
 16. The detector of claim 15, wherein the first winding isidentified when the angular value is substantially equal to about (180degrees±a tolerance value), the second winding is identified when theangular value is substantially equal to about (−60 degrees±the tolerancevalue), and the third winding is identified when the angular value issubstantially equal to about (+60 degrees±the tolerance value).
 17. Amethod for detecting a turn-to-turn fault in a three-phase shunt reactorcoupled to a three-phase power line system, the method comprising:receiving a first phase current measurement that is based on monitoringa first phase current flowing through a first winding of the three-phaseshunt reactor; receiving a second phase current that is based onmonitoring a second phase current flowing through a second winding ofthe three-phase shunt reactor; receiving a third phase currentmeasurement that is based on monitoring a third phase current flowingthrough a third winding of the three-phase shunt reactor; receiving afirst phase voltage measurement that is based on monitoring a firstphase voltage present on a first power line conductor of the three-phasepower line system; receiving a second phase voltage measurement that isbased on monitoring a second phase voltage present on a second powerline conductor of the three-phase power line system; receiving a thirdphase voltage measurement that is based on monitoring a third phasevoltage present on a third power line conductor of the three-phase powerline system; using each of the first phase current measurement, thesecond phase current measurement, the third phase current measurement,the first phase voltage measurement, the second phase voltagemeasurement, and the third phase voltage measurement and detecttherefrom, the turn-to-turn fault in at least one of the first winding,the second winding, or the third winding of the three-phase shuntreactor by calculating a difference value between a voltage-basedparameter and a current-based parameter, wherein the voltage-basedparameter is indicative of a normalized negative voltage imbalance andthe current-based parameter is indicative of a normalized negativecurrent imbalance; and declaring the turn-to-turn fault in at least oneof the first winding, the second winding, or the third winding of thethree-phase shunt reactor when the difference value is not equal tozero.
 18. The method of claim 17, wherein the voltage-based parameter isa first normalized value derived at least in part by comparing anegative sequence voltage value to a positive sequence voltage value,and the current-based parameter is a second normalized value derived atleast in part by comparing a negative sequence current value to apositive sequence current value.
 19. The method of claim 18, wherein thedifference value is defined as at least one of an absolute numericalvalue or an angular value, and an identification of the turn-to-turnfault in a particular one of the first winding, the second winding, orthe third winding of the three-phase shunt reactor is determined basedon the at least one of the absolute numerical value or the angularvalue.
 20. The method of claim 19, wherein the first winding isidentified when the angular value is substantially equal to about (180degrees±a tolerance value), the second winding is identified when theangular value is substantially equal to about (−60 degrees±the tolerancevalue), and the third winding is identified when the angular value issubstantially equal to about (+60 degrees±the tolerance value).